#include"sequence.h"
#include<vector>
#include<iostream>
using namespace std;
const int TREE_SIZE=1<<19;
int n;
vector<int>arr[500000];
int tree_lazy[2*TREE_SIZE];
int tree_min[2*TREE_SIZE];
int tree_max[2*TREE_SIZE];
void push_lazy(int node){
if(tree_lazy[node]!=0){
tree_min[node]+=tree_lazy[node];
tree_max[node]+=tree_lazy[node];
if(node<TREE_SIZE){
tree_lazy[2*node]+=tree_lazy[node];
tree_lazy[2*node+1]+=tree_lazy[node];
}
tree_lazy[node]=0;
}
}
int get_min(int node,int rl,int rr,int l,int r){
push_lazy(node);
if(r<=rl||rr<=l)
return 1e8;
if(l<=rl&&rr<=r)
return tree_min[node];
int mid=(rl+rr)/2;
return min(get_min(2*node,rl,mid,l,r),get_min(2*node+1,mid,rr,l,r));
}
int get_max(int node,int rl,int rr,int l,int r){
push_lazy(node);
if(r<=rl||rr<=l)
return -1e8;
if(l<=rl&&rr<=r)
return tree_max[node];
int mid=(rl+rr)/2;
return max(get_max(2*node,rl,mid,l,r),get_max(2*node+1,mid,rr,l,r));
}
int get_min(int l,int r){
return get_min(1,0,TREE_SIZE,l,r);
}
int get_max(int l,int r){
return get_max(1,0,TREE_SIZE,l,r);
}
void add(int node,int rl,int rr,int l,int r,int v){
push_lazy(node);
if(r<=rl||rr<=l)
return;
if(l<=rl&&rr<=r){
tree_lazy[node]+=v;
push_lazy(node);
return;
}
int mid=(rl+rr)/2;
add(2*node,rl,mid,l,r,v);
add(2*node+1,mid,rr,l,r,v);
tree_min[node]=min(tree_min[2*node],tree_min[2*node+1]);
tree_max[node]=max(tree_max[2*node],tree_max[2*node+1]);
}
void add(int l,int r,int v){
add(1,0,TREE_SIZE,l,r,v);
}
int sequence(int N,vector<int>A){
n=N;
for(int i=0;i<n;i++)
arr[A[i]-1].push_back(i);
/*for(int i=0;i<=n;i++)
tree[i]=-i;*/
for(int i=0;i<=n;i++)
add(i,i+1,-i);
int res=1;
for(int v=0;v<n;v++){
for(int idx:arr[v])
/*for(int i=idx+1;i<=n;i++)
tree[i]++;*/
add(idx+1,n+1,1);
int l=0;
for(int r=0;r<(int)arr[v].size();r++){
l=0;
int min2=get_min(arr[v][r],n+1);
int max2=get_max(arr[v][r],n+1);
int min1=get_min(0,arr[v][l]+1);
int max1=get_max(0,arr[v][l]+1);
while(l<r&&(max1+r-l+1<min2||max2+r-l+1<min1)){
l++;
min1=get_min(0,arr[v][l]+1);
max1=get_max(0,arr[v][l]+1);
}
res=max(res,r-l+1);
}
for(int idx:arr[v])
/*for(int i=idx+1;i<=n;i++)
tree[i]++;*/
add(idx+1,n+1,1);
}
return res;
}
